INVALIDOFFSET

INVALIDOFFSET is a symbolic constant used in computing to represent an invalid or undefined offset within a data structure, file, stream, or memory region. It serves as a sentinel value that signals that an offset cannot be determined or is outside the valid range.

Common representations of INVALIDOFFSET depend on language and API. It may be a negative value such as -1, or a large sentinel like SIZE_MAX or ULONG_MAX. Some libraries define a dedicated constant named INVALIDOFFSET or INVALID_OFFSET. In Windows, related semantics appear with INVALID_SET_FILE_POINTER, a value (0xFFFFFFFF) used to indicate a failure in a file-seeking operation; in POSIX-like interfaces, error signaling is typically expressed by returning -1 from functions like lseek, with errno set accordingly.

Semantics and usage: When a function returns INVALIDOFFSET, the result should be treated as an error rather than a valid position. Handling usually involves checking the sentinel before using the offset in I/O or memory access, and then propagating or translating the condition into a descriptive error status for the caller.

Considerations: Offsets may be 32-bit or 64-bit, so the choice of sentinel must be compatible with the address space in use. Using a sentinel value can risk collision with valid offsets, especially in large datasets. Some modern APIs avoid sentinel offsets by returning a separate status indicator or an optional/result type that clearly distinguishes success from failure.

See also: offset, file pointer, seek, sentinel value, error handling.